Electromagnetic device



July 7, 1936. H. M. STOLLER ELECTROMAGNETIC DEVICE Filed Sept. 28, 1932 I l B I INVENTOR H.114. STOLLER Mam 6' M Patented July 7, 1936 UNl'lE sr'r PATEN OFFICE ELECTROMAGNETIC DEVICE Hugh M. Stoller, Mountain Lakes, N. 3., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application September 28, 1932, Serial No. 635,160

8 Claims. OCH. 177-7) This invention relates to electromagnetic deof thesynchronous motor of the device of this vices and more particularly to alternating curinvention. rent signaling devices for telephone substa- Referring now to the drawing. the ringer intions. cludes a flanged mounting bracket or base II] An object of the invention is to obtain a speof non-magnetic material, such as brass, upon cific reduction ratio between the frequency of which a pair of excitation coils are mounted, the impressed signaling current and the freeach including a core ll, only one of which is quency of the final ringing impulse whereby a shown, and a winding l2. The coils are sesingle stroke ringer may be operated by the cured to the bracket or base In together with 10 usualcentral oilice equipment. L-shaped magnetic poles l3 by machine screws 1 In one embodiment of this invention, an alter- It which extend through the bracket or base nating current ringer comprises a self-starting and the poles and are threaded into the cores H. synchronous motor, a percussion member cou- A non-magnetic stamping or plate l5 which pled to the rotor thereof, a retractile spring conmay be of brass, is mounted upon the opposite nected to the percussion member and to a staends of the cores i l, as shown more clearly in l tionary support, and an audible signaling de- Fig. 3, and has mounted thereon a plurality of vice, such as a gong, adapted to be actuated by stator segmental magnetic members or polethe percussion member. When an excitation pieces. Two of these members comprise a sectorcurrent is applied to the motor, the rotor is shaped base it and a plurality of integral milled advanced in step automatically and revolves in teeth or segments l'l extending vertically on 20 one direction, carrying with it the percussion one edge of the base I 6;. The base portions l6 member against the action of the retractile are secured to the cores H by machine screws spring. The spring is of such construction that it and are secured to the stamping l5 by pins after the rotor has revolved through a predeor rivets l9. Another pair of magnetic memtermined arc, the tension in the spring overbers provided witha sector-shaped base 20 which comes the motor torque and forces it out of is secured to the stamping l5 by pins or rivets synchronism. Upon loss of synchronism the mo- 25 have a plurality of uniformly spaced milled tor torque drops to a fraction of its synchro-= teeth or segments 22 which engage with the nous value and the retractile spring revolves the poles I 3. The se men s and as Shown percussion member and the rotor at high vemore clearly in Fig. 4, are disposed on the cir- 30 locity in the reverse direction until the percumference of a circle and form the pole pieces cussion member strikes a push rod or clapper of the stator of a synchronous motor. for sounding the signal gong. The rotor there- The rotor of the motor is disposed concenupon is advanced in step and the sequence of trically within the teeth or segments l7 and 22 operations is repeated. The motor and spring and comprises a fiat disc 23 of magnetic mate- 35 are so constructed and correlated that the signal rial, such as iron, having a plurality of periphgong is struck at relatively widely separated eral teeth or segments 25 which have the same intervals. spacing or pitch as the segments H and 22 and 40 The invention and the various features therean axially disposed hub 25. The hub 25 is proof will be understood more clearly and fully from vided with an axial bore 28 through which a 40 the following detailed description with referreduced portion 29 of a bearing pin extends. ence to the accompanying drawing in which: The bearing pin is provided with a portion 3!! Fig. 1 is a perspective vview in elevation of which is threaded into an arm 3| of the stampan alternating current ringer illustrative of one ing I5 and has mounted thereon a lock nut 32 embodiment of this invention with parts broken for securing the bearing pin in position. The 45 away to show details of assembly more clearly; other end 26 of the pin fits into a bore 2'! in the Fig. 2 is a top view of the ringer shown in stamping B5. A percussion member, preferably Fig. l; of metal, is loosely mounted upon the reduced Fig. 3 is an exploded view of the ringer of portion 2a of the bearing pin and comprises a this invention shown partly broken away and .hub 33, an arm 34, and an enlarged head or 50 partly in section to illustrate the relation of the hammer. 35. The percussion member is resilistator and rotor of the motor and'the other ently coupled to the rotor by a bent wire 36, elements of the device; and shown more clearly in Fig. 2, which is secured Fig. 4 is a diagrammatic view showing the to the head or hammer 35 atone end, and to relative disposition of the stator and rotor teeth a stud 31 mounted on the rotor at the other end.

, the poles l3, pole pieces 2b, 22,

arm 6!! by a helical torsion spring it.

The percussion member is also connected to the bearing pin 29 by a spiral spring 38 which is contracted by the clockwise rotation of the per cussion memmr and the rotor 23.

A push rod or clapper 39 for striking a signaling member such as a spiral spring gong db extends slidably through parallel arms ii and d2 of the stamping l5 and is connected to the such as a set screw 36, is mounted limits the movement of the d6 of felt or the'like.

"The rel'ative positioning of the segments on the stator pole pieces and on the rotor is shown diagrammatically in Fig. 4, in which the groups of segments i? are designated generally as A and D and the groups of segments 22 aredesignated generally as B and C. From this figure it will be. seen that when the stator segments constituting group C are in alignment with the juxtaposed segments of the rotor, the stator segments constituting group D are in alignment with the interstices between the juxtaposed rotor segments. Likewise, the stator segments constituting group A are advanced a quarter pitch ahead of the adjacent rotor segments while the stator segments constituting group B are displaced one quarter pitch behind the corresponding rotor segments. The coils H are preferably connected in series, one of the coils being shunted by a condenser (not shown) so that the currents through the coils iii are 90 out of phase.-

When an excitation current, such as a 2!! cycle ringing current usually employed in central oflice telephone equipment, is supplied to the coils, the rotor is pulled into step automatically and revolves at a speed determined by the stator field divided by the number of rotor segments. As-

suming for'illustration a point in the current cycle corresponding to the position of the rotor shown in Fig. 4, that is when the current is a maximum in the coil corresponding to the poles C and D and a minimum in the coil corresponding to the poles A and B,'the rotor segments in juxtaposition to the stator segments of group C are in alignment, and the torque effective between the rotor and the stator segments of group. C has reached a maximum, while the torque effective between the rotor and the stator segments of group D is a minimum. The only flux between the rotor and the stator segments constituting groups A and B is that of the biasing magnet t5 so that the torques between the rotor and the stator segments A and B are counterbalanced. At the end of the next succeeding quarter cycle of excitation current the rotor has revolved in a clockwise direction so that the rotor segments are in alignment with the stator segments A, one-half pitch out of alignment with the segments B, and'one' quarter pitch out of alignment with each of the segments of groups C and D. At this point the torque effective-between the segments of the rotor and the segments of group A has reached a maximum, while the torque effective between the segments of the rotor and the stator segments B is a An adaosaroe torques effective between the of groups C and minimum. The rotorand the stator segments v D are then counterbalanced. On succeeding quarter cycles the torque between the rotor and the stator teeth D reaches a maximum and then between the rotor and the stator teeth of group The sequence of operations of the ringer described is as follows: When an excitation current is applied to the coils t2, the rotor automatically advances in step and revolves in a clockwise direction carrying with it the percussion member 35 so that the spiral spring 38-is wound up or stressed. When the rotor has revolved through a predetermined arc, the tension in the spring 38 becomes greater than the motor torque and as a result the motor is forced out of synchronism and its torque reduced thereby permitting the torsion spring 38 to assume control and the spring then rotates the percussion member and the rotor at high velocity in a counter-clockwise direction. The head or hammer 35 strikes the end of the push rod 39) to actuate the signal gong 453. After the gong is struck the rotor again advances in step and the sequence of operations is repeated.

The motor and spiral torsion spring 38 may be so constructed that the' signal gong to will be actuated at any desired intervals. For example, the signaling device shown and described may be operated by 20 cycle ringing current which may be applied for two seconds at four second intervals. The rotor may have a speed of one-half revolution per second so that the gong Mi will be actuated at intervals of approximately six seconds. 4

Although a specific embodiment of the invention has been shown and described, modifications may be made, of course, without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. An alternating current signal gong, a rotatable member for actuating said gong, a self-starting synchronous motor including a rotor coupled to said member, and'a retractile spring flxed at one end and connected to said member capable when stressed by rotation ofsaid rotor of overcoming the motor torque, said motor and said spring being effective alternately to revolve said member in opposite directions whereby said gong is actuated periodically.

2. An electromagnetic signaling device comprising-a signal gong-striking means for said gong, a self-starting synchronous motor having a rotor for revolving said means. and an elastic member couplied to said rotor and adapted to be ringer comprising a when stressed to overcome the torque acting on said rotor and to revolve said rotor and said striking means in the opposite direction to actuate said gong.

4. An alternating current ringer comprising a stressed by revolution of said rotor in one direcv signaling member, means for actuating said member, a self-starting synchronous motor having a stator and arotor, a mass member coupled to said rotor, and an elastic member connected to said mass member and adapted to be stressed by rotation of said mass member in one direction, .said elastic member being effective when stressed to a predetermined degree to overcome the motor torque and to revolve said mass member in the opposite direction to impinge on said actuating means.

5. An alternating current ringer comprising a signal gong, striking means for said gong, a selfs'tarting synchronous motor including a stator, a shaft, and a rotor mounted on said shaft, a percussion member for actuating said striking means rotatably mounted on said shaft and coupled to said rotor, and a spiral spring having a fixed portion and connected to said percussion member and adapted to be tensioned by rotation of said rotor in one direction, said spring being effective when tensioned to a predetermined degree to overcome the motor torque and to revolve said percussion member in the opposite direction to actuate said striking means.

6. An alternating current ringer comprising a self-starting synchronous motor including a rotor, a percussion member coupled to said rotor, signaling means, and a retractile spring fixed at being effective when stressed to overcome the torque acting on said percussion member and to revolve said percussion member in the opposite direction to actuate said signaling means.

7. A signaling device comprising a signal gong, a clapper for actuating said gong, a shaft, a rotatable member mounted on said shaft, a selfstarting synchronous motor having a rotor mounted on said shaft, and coupled to said member, and elastic means connected to said member, said elastic means being adapted to be stressed by rotation of said member in one direction and effective when stressed to a predetermined degree and while said motor is energized to revolve said member in the opposite direction to actuate said clapper.

8. A signaling device'comprising a signal gong, means for actuating saidgong, and means for actuating said first means including a self-starting synchronous motor having a rotor cooperat ing withsaid first means and a spring fixed at one end and coupled to said rotor at the other end and operable to reverse the direction of rotation of said rotor periodically.

HUGH M. STOILER. 

